Atrial fibrillation is a condition that affects large groups of people with new patients being diagnosed each year. These patients have a lower quality of life as well as having up to a seven times increase in the likelihood of heart attacks or strokes. Current therapies include drug treatment or defibrillation, both palliative forms of treatment. Over the past few years, a number of research groups have been investigating curative treatment involving ablative techniques using radio frequency (RF), ultrasound, laser or microwave energy or cryoablation techniques.
Ablation therapy, while being promising, requires complex catheter designs. Such catheters also have to be reasonably thin to be manoeuvred through a patient's vascular system.
A current approach is the use of a catheter in the shape of a lasso which has a number of electrodes used for diagnostic purposes only. The lasso is positioned through the left atrium of the heart in pulmonary veins. As the lasso is round in shape, it surrounds the inside of the vein. Different sizes of catheters are required depending on the size and shape of the ostium. A typical procedure uses a first catheter to sense regions of irregular electrical activity and a second, separate, ablation catheter to ablate the specific site of irregular electrical activity. The procedure is repeated at various sites until all sites of irregular electrical activity have been blocked. One of the disadvantages associated with this procedure is the difficulty in guiding the ablation catheter to the exact site of the vein at which ablation is to occur. In this regard, it must be borne in mind that the first catheter which is used to sense the irregular electrical activity needs to be retained in position while the second catheter is inserted through the patient's vascular system to the site to guide the ablation catheter to that site. In addition, too much energy can lead to excessive tissue damage which can lead to stenosis of the blood vessel. Conversely, too little energy or insufficient ablated sites can lead to a re-occurrence of the irregular, electrically conductive pathways and therefore the likelihood of further atrial arrhythmia.